fix: agentic loop robustness — tool arg sanitisation, geocoding, better errors

- Sanitise tool call arguments before re-sending in conversation history: non-object values (bool, string, null) that some models produce are normalised to {} to prevent Ollama 500s
- Map 'error parsing tool call' Ollama 500 to HTTP 400 with a descriptive message listing compatible models (llama3.1, llama3.2, qwen2.5, mistral-nemo)
- Add reverse_geocode tool backed by existing Nominatim helper; description hints model can chain it after get_location_history results
- Make get_sms_messages contact parameter optional (was required, forcing the model to guess); executor now passes None to fall back to all-contacts search
- Log tool result outcomes at warn level for errors/empty results, info for successes; log SMS API errors with full detail; log full request body on Ollama 500
- Strengthen system prompt to require 3-4 tool calls before final answer
- Try fallback server when checking model capabilities (primary-only check caused 500 for models only on fallback)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ai/ollama.rs

@@ -591,6 +591,10 @@ Analyze the image and use specific details from both the visual content and the
             options,
         };
 
+        let request_json = serde_json::to_string(&request_body)
+            .unwrap_or_else(|e| format!("<serialization error: {}>", e));
+        log::debug!("chat_with_tools request body: {}", request_json);
+
         let response = self
             .client
             .post(&url)
@@ -602,6 +606,11 @@ Analyze the image and use specific details from both the visual content and the
         if !response.status().is_success() {
             let status = response.status();
             let body = response.text().await.unwrap_or_default();
+            log::error!(
+                "chat_with_tools request body that caused {}: {}",
+                status,
+                request_json
+            );
             anyhow::bail!(
                 "Ollama chat request failed with status {}: {}",
                 status,